A tooth is comprised of an outer hard enamel protective layer surrounding an inner dentin layer. The outer enamel layer is composed of apatite mineral crystals that are somewhat porous. Plaques, which can contain 250 or more separate microbial species, are a major cause of dental decay. These plaques use sugars and other fermentable carbohydrates to produce acids, which cause demineralization of the tooth surface. In its initial stages, a carious lesion is not readily apparent. However, with prolonged and repeated demineralization by plaque-created acids, a cavity will ultimately form at the lesion site.
When a lesion or cavity develops on the surface of a tooth, a dentist traditionally fills it, in order to prevent further spread of the decay. However, this procedure does not restore the tooth to its original state. Thus, a considerable amount of research has been directed toward the remineralization of dental lesions, with the primary objective being the deposition and/or formation of tooth mineral lost through decay. Through remineralization (e.g., with hydroxyapatite, optionally containing other ingredients such as fluoride), the tooth is not merely repaired, but restored to its original form.
Various approaches to remineralization and topical fluoridation are described, for example, in the background of U.S. Pat. No. 6,000,341 and related patents and patent applications. The '341 patent itself teaches the use of amorphous calcium phosphate compounds, such as amorphous calcium phosphate (ACP), amorphous calcium carbonate phosphate (ACCP), amorphous calcium phosphate fluoride (ACPF), and amorphous calcium carbonate phosphate fluoride (ACCPF) for use in remineralizing teeth.
Other routes for achieving tooth remineralization are described in U.S. Patent Application Publication No. 2006/0110340, where, for example, separate compositions comprising one or more soluble calcium, orthophosphate, and peroxide salts may be stabilized for storage and then activated upon use. Also, U.S. Patent Application Publication No. 2005/0281759 describes the synthesis and use of calcium peroxyphosphate compounds, in dental compositions for whitening, mineralizing, and/or fluoridating teeth.
There is an ongoing need in the art for compositions that can remineralize teeth by filling voids associated with tooth decay, mechanical injury, or even organic stain removal. The potential for dental remineralization as an alternative to conventional treatment methods is vast, since dentists currently fill millions of cavities each year. If these cavities were remineralized rather than filled, the general dental health of the public would improve. This is apparent because remineralization, unlike traditional cavity filling, effectively results in a whole tooth.
Nanoparticles have recently become a topic of considerable scientific interest, as they represent a “bridge” between bulk materials and molecular or atomic structures. While bulk materials of standard dimensions have constant physical properties regardless of size, this relationship often breaks down on the nano-scale, as surface effects become more pronounced. Eventually, for particulates having dimensions on the atomic scale, these surface effects will dominate, often with unpredictable results. For example, conventionally sized copper wire bends easily because of the movement of bulk copper atoms/clusters. In contrast, copper nanoparticles are extremely hard materials that do not exhibit the same malleability and ductility. Other properties, such as particulate solvent interactions, diffusion, agglomeration, and even color, may vary considerably in the case of nanoparticles, relative to their respective bulk materials.
The use of nanotechnology in the treatment and prevention of diseases holds great promise. However, many practical considerations associated with medical and dental applications are relevant, including biocompatibility, toxicity, and functionality under physiological conditions. While calcium, phosphate and fluoride salts have been used for tooth remineralization, previous compositions and methods utilizing these components do not form or involve the use of nanoaggregates.